Helio HT-295 N18JC accident near Marion, Ohio

Probable cause

The failure of the right main landing gear spring due to intergranular stress-corrosion cracking that progressed into fatigue. Contributing to the accident was the improper rework of the spring at an undetermined time.

NTSB analysis

The pilot reported that, after a normal landing, the pilot heard a “pop” followed by a leaning tendency to the right that he attempted to correct with flight control inputs. He could not arrest the right turn, and the airplane departed the right side of the runway and came to a stop, upright, in the grass. The right wing and right stabilator sustained substantial damage.

The right main landing gear spring separated during the landing roll. Metallurgical examination of the spring revealed evidence of chloride intergranular stress-corrosion cracking that progressed into fatigue over time. The examination also found evidence of the spring being reworked after manufacture, with grinding marks perpendicular to the lengthwise direction of the part (contrary to manufacturer-approved procedures), areas of missing paint, and corrosion pitting. The operator reported that the spring had not been removed or reworked since they purchased the airplane more than 25 years before the accident.

Text from the NTSB. Open the NTSB docket for ERA25LA091 for the full record.